First version of PerformanceObserver

Source/core/timing/PerformanceUserTiming.h

 /*
  * Copyright (C) 2012 Intel Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 23 matching lines @@
 namespace blink {
 
 class ExceptionState;
 class PerformanceBase;
 
 typedef unsigned long long (PerformanceTiming::*NavigationTimingFunction)() const;
 using PerformanceEntryMap = HeapHashMap<String, PerformanceEntryVector>;
 
 class UserTiming final : public GarbageCollected<UserTiming> {
 public:
-    static UserTiming* create(PerformanceBase* performance)
+    static UserTiming* create(PerformanceBase& performance)
     {
         return new UserTiming(performance);
     }
 
-    void mark(const String& markName, ExceptionState&);
+    PerformanceEntry* mark(const String& markName, ExceptionState&);
     void clearMarks(const String& markName);
 
-    void measure(const String& measureName, const String& startMark, const String& endMark, ExceptionState&);
+    PerformanceEntry* measure(const String& measureName, const String& startMark, const String& endMark, ExceptionState&);
     void clearMeasures(const String& measureName);
 
     PerformanceEntryVector getMarks() const;
     PerformanceEntryVector getMeasures() const;
 
     PerformanceEntryVector getMarks(const String& name) const;
     PerformanceEntryVector getMeasures(const String& name) const;
 
     DECLARE_TRACE();
 
 private:
-    explicit UserTiming(PerformanceBase*);
+    explicit UserTiming(PerformanceBase&);
 
     double findExistingMarkStartTime(const String& markName, ExceptionState&);
 
     Member<PerformanceBase> m_performance;
     PerformanceEntryMap m_marksMap;
     PerformanceEntryMap m_measuresMap;
 };
 
 } // namespace blink
 
 #endif // !defined(PerformanceUserTiming_h)